Aluminum base alloy containing copper, nickel, and silicon



Patented Aug. 1, 19.33

ALUMINUM. BASE ALLOY CONTAINING COPPER, NICKEL, AND SILICON Walter A.Dean, Cleveland, Ohio, assignor to Aluminum Company of America,Pittsburgh, 'Pa., a Corporation of Pennsylvania No Drawing. ApplicationJuly 22, 1931. Serial No. 552,557

3 Claims. (01. 15-1.)

This invention relates to aluminum base alloys designed to meet theproblems encountered in the manufacture of articles which must withstandhigh temperatures without-plastic de- 5 formation or a comparativelylarge loss of strength, as for example, the manufacture of pistons forinternal combustion engines, more particularly the invention relates toaluminumsilicon-copper-nickel alloys, with or without one or more of theelements titanium, molybdenum, tungsten, manganese, chromium and iron.

Somewhat similar alloys have already been disclosed in a copendingapplication of R. S. Archer and L. W. Kempf, Serial No. 403,353, filedOctober 29, 1929. The present invention constitutes an alloy of thisclass of greatly improved tensile strength in the cast condition, higherimpact resistance at elevated temperatures, and more refined crystallinestructure.

0 In the above-mentioned copending application, aluminum base alloyswere disclosed and claimed containing 6 to 8 per cent nickel, 6 to 8 percent silicon, and 6 to 8 per cent copper and characterized in particularby low thermal ex-.

pansivity, improved strength at high temperatures, and high modulus ofelasticity. Th'ese desirable properties are commercialized specificallyinto pistons for internal combustion engines or other uses where thearticles are subjected to stress at relatively high temperatures. I havefound that if the composition be modified so that the alloy containsless than 6 per cent but not less than about 2 per cent of nickel, thetensile strength in the cast condition is raised;

the crystalline structure 'is more refined, and the ductility of thealloy is increased, without material impairment of any of the advantageswhich characterized the former commercial composition disclosed in theaforesaid application. I

L0 have also found that the copper and silicon contents can be decreasedto about 5 per cent without impairing the advantageous properties of thealloy.

As an example, an aluminum base alloy containing 'l per cent copper, '7per cent silicon, and 7 per cent nickel has an impact value of about 39foot pounds per square inch at 600 degrees Fahrenheit, and the impactvalue of one of my alloys containing 7 per cent copper, '7 per centsilicon, and 4 per cent nickel under the same conditions is foot poundsper inch or an per cent increase in-impact resistance. This comparisonis derived from the results of a series of liightemperature tests madeon a Charpy impact testing machine adapted to high temperature work. Ahigh impact resistance at elevated temperatures signifies an ability towithstand severe shock at elevated temperatures, a property very usefulwhen the alloy used is in the form of a piston in-internal combustionengines.

The tensile strength of an alloy of '7 per cent copper, 7 per centnickel and 7 per cent silicon is about 17,000 pounds per square inch inthe ascast condition. The tensile strength of one of my improved alloysin which the nickel is reduced to 4 per cent, the copper and siliconremaining at 7 per cent each, is about 26,000 pounds per square inch.

I have discovered, in addition, that the hardness of my alloys atelevated temperatures may be improved by adding from about 0.01 per centto 1.0 per cent of a high melting point metal, for instance titanium,molybdenum, tungsten, manganese, chromium, or iron, without sensiblyimpairing other useful properties of the alloys 75 and even, in somecases, effecting considerable improvement in characteristics such asgrain size. More than one of these high melting point metals may be usedin combination provided their total amount does not exceed about 1 percent of the whole.

The alloys which are the subject of the present invention may be heattreated for the purpose of improving their tensile and hardnessproperties or they may be otherwise thermally treated for the purpose ofremoving strains or stabilizing volume changes. For such purposes, theheat treatment and other thermal processes well known to those skilledin the art may be temperature solution heat treatment and the lowertemperature aging treatment now widely recognized as being beneficial inthe case of certain aluminum base alloys.

The term "aluminum-sllicon-copper-nickel alloy is used herein and in theappended claims as including the following, and none other: (a) Alloysconsisting of the four elements named, in the proportions stated in theclaims; and (1)) Alloys consisting of the four elements named, in theproportions stated in the claims, and one or more of the metalstitanium, molybdenum, tungsten, manganese, chromium and iron, in totalamount from about 0.01 to 1 per cent.

Having thus described and explained my invention, what I claim is- 1. Analuminum-silicon-copper-nickel alloy in which the elements named are insubstantially thefollowing proportions: Nickel2 to 4 per cent,

copper 5 to 8 per cent, silicon 5 to 8 per cent, and aluminum 7'! to 88per cent.

2. An aluminum-silicomcopper-nickel alloy in which the elements namedare in substantially I not less than 81 per cent.

4. An aluminum-silicon-copper-nickel alloy in which the elements namedare in the proportion of nickel 4 per cent, copper '7 per cent, silicon7 per cent, aluminum at least 81 per cent; the alloy containing also atleast one metal of the class composed of titanium, molybdenum, tungsten,manganese, chromium and iron, the total amount of metal of said classbeing about 0.01 to 1 per cent.

5. A piston formed of an aluminum base alloy consisting of aluminum,about 5 to 8 per cent silicon, about 5 to 8 per cent copper, not less'than about 2 but less than 6 per cent nickel, aluminum at least 77 percent, and at least one metal of the class composed of titanium,molybdenum, manganese, chromium, tungsten and iron, the total amount ofmetal 01' said class being from about 0.01 to 1 per cent.

6. A piston formed of an aluminum-silicone,

copper nickel alloy in which the elements named are in substantially thefollowing proportions: nickel 4 per cent, copper 7 per cent, silicon 7per cent, and aluminum at least 81 per cent.

. WALTER A. DEAN.

